Das for multi-frequency band and multi-carrier based on o-ran standard

ABSTRACT

A distributed antenna system (DAS) for multi-carrier and multi-frequency band based on an O-RAN standard in an open radio access network (O-RAN)-based mobile communication network is provided. The DAS includes an O-RAN remote unit (RU) connected to a fronthaul network according to an O-RAN split option specification of base station transceiver systems (BTSs), and comprising a plurality of O-RAN RUs to accommodate a plurality of carriers and a plurality of frequency bands, and a channel combiner to which outputs of the plurality of O-RAN RUs are combined. The channel combiner is an analog combiner. The DAS further includes an optical distribution unit (ODU) connected to the analog combiner, and a radio unit (RU) connected to the ODU. The RU includes an optical receiving unit (ORU), a high power amplifier (HPA), a low noise amplifier (LNA), and a duplexer or filter.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a divisional application of U.S. Pat. No. 17,528,461filed on Nov. 17, 2021, which claims priority to Korean PatentApplication No. 10-2021-0116402 filed on Sep. 1, 2021, the entirecontents of which are herein incorporated by reference.

BACKGROUND 1. Field

The present disclosure relates to a distributed antenna system (DAS) formulti-frequency band and multi-carrier equipped with an open radioaccess network (O-RAN) remote unit (RU) according to an O-RAN technologystandard for building a next-generation radio infrastructure.

2. Description of the Related Art

The open radio access network (O-RAN) standard empowered by principlesof intelligence and openness is the foundation for building thevirtualized RAN on open hardware and cloud with AI-powered radiocontrol. The O-RAN standard was created to ensure a wide range ofsupplier community driven by innovation and open market competition andsimultaneously accelerate the delivery of products that support commonand open architecture and standardized interface that we, as carriers,regard as the foundation of next-generation radio infrastructure.

In building the next-generation radio infrastructure through the O-RANstandard, the O-RAN remote unit (RU) is developed as a RU for a specificfrequency band or a specific carrier like the existing base stationsystem, develops these products and supplies the products to a specificcarrier.

However, in a market environment in which the radio infrastructure is tobe built, it is necessary to simultaneously service multi-carrier andmulti-frequency band. Therefore, distributed antenna system (DAS)equipment to accommodate multi-frequency band and multi-carrier isrequired.

FIG. 1 is a schematic block diagram of a conventional DAS. As shown inFIG. 1 , a plurality of base station transceiver systems (BTS) 0 and 20are respectively connected to POIs 30 and 40 by RF signals, and the RFsignals of the POIs 30 and 40 are combined to multi-band by a channelcombiner (CHC) 50. Then, the RF signal of the multi-band is distributedto radio units (RUs) 70 by an optical distribution unit (ODU) 60.

In order to combine the O-RAN to the conventional DAS, there may be asolution to receive an RF signal generated through central unit(CU)-distribution unit (DU) and RU that is an O-RAN-based base station,but such a configuration is different from the open architecture andstandardized interface of the O-RAN concept, and the cost is raised dueto the configuration. Therefore, there is a need for a structure thatcan simultaneously service multi-frequency band and multi-carrier byaccommodating a function of O-RAN RU in the DAS by utilizing a splitstandard between DU-RU and simultaneously accommodating a plurality ofO-RAN RUs in the form of CU-DU-RU which is the O-RAN-based base station.

PRIOR ART DOCUMENT

[Patent Literatures]

-   1. Korean Patent Application No. 10-2018-0061358 (Wireless    beamforming device that minimizes power loss in millimeter wave    band)-   2. U.S. Pat. No. 10,701,755 (Wireless communications using    virtualized base stations network).

SUMMARY

Although the existing DAS uses an RF signal or a digital common publicradio interface (CPRI) method to exchange signals with a base station,there is a need for a structure that can service multi-frequency bandand multi-carrier by accommodating a function of O-RAN RU in the DAS byutilizing a split standard between DU-RU from the form of CU-DU-RU whichis an O-RAN-based base station. Furthermore, there is a need for astructure that can accommodate a plurality of O-RAN RUs to provideservice for multi-carrier and multi service provider, which is not thestructure that only provide a service for a specific frequency or aspecific carrier between DU-RU.

It is possible to directly install the O-RAN-based RU in a distributedregion without through the DAS, but the product price increases becausea function of a complex O-RAN interface and a function of a low physicallayer exist in all RUs. Therefore, the present disclosure is directed toproviding a distributed antenna system (DAS) for multi-carrier andmulti-frequency band based on an open radio access network (O-RAN)standard in which an O-RAN remote unit (RU) function is combined to theDAS.

The problems to be solved of the present disclosure are not limited tothe description mentioned above, and other technical problems that arenot mentioned will be clearly understood by those skilled in the artfrom the following description.

In one aspect of the present disclosure, there is provided a distributedantenna system (DAS) for multi-carrier and multi-frequency band based onan O-RAN standard in an open radio access network (O-RAN)-based mobilecommunication network, the DAS including an O-RAN remote unit (RU)connected to a fronthaul network according to an O-RAN split optionspecification of base station transceiver systems (BTSs), and includinga plurality of O-RAN RUs to accommodate a plurality of carriers and aplurality of frequency bands; and a channel combiner to which outputs ofthe plurality of O-RAN RUs are combined.

The O-RAN RU may include an O-RAN interface configured to communicatewith the fronthaul network and meet the O-RAN split optionspecification; a low physical layer configured to process a signal ofthe O-RAN interface; an analog-to-digital converter (ADC) anddigital-to-analog converter (DAC) corresponding to a form of the channelcombiner; and an up/down converter (UDC) configured to convert aconverted signal into radio frequency (RF).

The O-RAN interface may be an Ethernet or optical interface.

The channel combiner may be at least one of an analog combiner and adigital combiner.

The channel combiner may be the analog combiner, and the DAS may furtherinclude a POI interface for connection by an analog RF signal.

The channel combiner may be the digital combiner, and the DAS mayfurther include a digital common public radio interface (CPRI)/open basestation initiative (OBSAI) interface.

The channel combiner may be the analog combiner, and the DAS may furtherinclude an optical distribution unit (ODU) connected to the analogcombiner; and a radio unit (RU) connected to the ODU, and the RU mayfurther include an optical receiving unit (ORU) configured to receive anoptical signal from the ODU; a high power amplifier (HPA) configured toprocess the received optical signal; a low noise amplifier (LNA)configured to process the received optical signal; and a duplexer orfilter configured to transmit an output of the HPA and an output of theLNA as radio waves.

An output signal of the analog combiner may be a signal equal to or lessthan 6 GHz.

The channel combiner may be the analog combiner, and the DAS may furtherinclude an ODU connected to the analog combiner; and a millimeter waveRU connected to the ODU, and the millimeter wave RU may include an ORUconfigured to receive an optical signal from the ODU; an IF-RF converterconfigured to convert an output of the ORU into an intermediatefrequency (IF) and then convert the IF into RF; an RF-millimeter waveconverter configured to receive the RF; an array antenna interfaceconnected to the RF-millimeter wave converter; and an array antennaconnected to the array antenna interface to perform broadbandtransmission.

The RF may be equal to or greater than 6 GHz.

The millimeter wave frequency may accommodate multi-frequency.

According to the present disclosure, it is possible to accommodate aplurality of O-RAN RUs of the O-RAN standard limited to a specificfrequency in a specific frequency band and a specific carrier in onesystem, and thus the O-RAN RU may be efficiently used for the DAS formulti-frequency band and multi-carrier.

In addition, it is possible to effectively build an O-RAN infrastructurewithout adding a function of a complex O-RAN interface and a function ofthe low physical layer for each of the plurality of O-RAN RUs that areinstalled in a distributed manner, and thus the O-RAN RU is technicallysimple, and in terms of cost, may be implemented and operated at a lowcost.

In addition, when accessing a network in which the O-RAN DU-RU splitoption is changed, the interface needs to be changed. In this case, onlythe function of the O-RAN RU needs to be changed, and thus only theO-RAN interface needs to be changed without a great burden on the systemchange.

In addition, there is an advantage of accommodating various technologiessuch as POI which is responsible for transmitting and receiving theconventional analog RF signal and a method of receiving the digitalsignal together in the location of the O-RAN RU.

The effects of the present disclosure are not limited to the descriptionmentioned above, and other effects not mentioned will be clearlyunderstood by those skilled in the art from the following description.

BRIEF DESCRIPTION OF DRAWINGS

The following drawings attached to the specification illustratepreferred embodiments of the present disclosure, and serve to furtherunderstand the technical spirit of the present disclosure together withthe detailed description of the present disclosure to be describedlater, so that the present disclosure should not be construed as beinglimited only to the matters described in such drawings.

FIG. 1 is a schematic block diagram of a conventional distributedantenna system (DAS);

FIG. 2A is a schematic block diagram of a distributed antenna system(DAS) connected to a channel combiner by an analog RF signal by applyinga function of an O-RAN-based remote unit (RU) according to an embodimentof the present disclosure;

FIG. 2B is a schematic block diagram of a DAS connected to a digitalchannel combiner by a digital baseband I/Q signal by applying a functionof an O-RAN-based RU according to an embodiment of the presentdisclosure;

FIG. 2C is a schematic block diagram of a DAS according to anotherembodiment of the present disclosure;

FIG. 3 is a schematic block diagram of an O-RAN-based mobilecommunication access network;

FIG. 4 is a schematic block diagram of a DAS applicable to equal to orless than 6 GHz according to an embodiment of the present disclosure;and

FIG. 5 is a schematic block diagram of a DAS applicable to a millimeterwave according to an embodiment of the present disclosure.

DETAILED DESCRIPTION

Hereinafter, with reference to the accompanying drawings, theembodiments of the present disclosure will be described in detail sothat those skilled in the art may easily implement the embodiments.However, since the description of the present disclosure is merely anembodiment for structural or functional description, the scope of thepresent disclosure should not be construed as being limited by theembodiment described in the specification. That is, since the embodimentmay have various changes and forms, it should be understood that thescope of the present disclosure includes equivalents capable ofrealizing the technical idea. In addition, since the object or effectpresented in the present disclosure does not mean that a specificembodiment should include all of them or only such effects, the scope ofthe present invention should not be construed as being limited thereby.

The terms described in the present disclosure should be understood asfollows.

Terms such as “first” and “second” are for distinguishing one elementfrom another, and the scope of rights should not be limited by theseterms. For example, a first element may be referred to as a secondelement, and similarly, a second element may also be referred to a firstelement. When an element is referred to as being “connected” to anotherelement, it may be directly connected to the other element, but itshould be understood that other elements may exist therebetween,whereas, when it is mentioned that a certain element is “directlyconnected” to another element, it should be understood that the otherelement does not exist therebetween. Meanwhile, other expressionsdescribing the relationship between elements, that is, “between” and“directly between” or “adjacent to” and “directly adjacent to”, etc.,should be interpreted similarly.

As used herein, the singular forms also are intended to include theplural forms as well, unless the context clearly indicates otherwise. Itwill be further understood that the terms “comprises” and/or“comprising,” when used in this specification, specify the presence ofstated elements, steps, operations, and/or components, but do notpreclude the presence or addition of one or more other elements, steps,operations, and/or components.

All terms used herein have the same meaning as commonly understood bythose skilled in the art, unless otherwise defined. Terms defined ingeneral used in the dictionary should be interpreted as having themeaning consistent with the context of the related art, and cannot beinterpreted as having an ideal or excessively formal meaning unlessexplicitly defined in the present disclosure.

Hereinafter, embodiments of the present disclosure will be described indetail with reference to the accompanying drawings.

An O-RAN RU 200 is provided between an O-RAN-based mobile communicationbase station fronthaul network 100 and a channel combiner 120, and iscapable of processing the O-RAN-based split 7.2X standard. The O-RAN RU200 is configured to communicate with the fronthaul network 100, andbasically includes an O-RAN interface 210 of the O-RAN split 7.2Xstandard and a low physical layer Low-PHY 212 for processing a signal ofthe O-RAN interface 210. Here, there may be methods of combiningmulti-frequency band and multi-carrier signal into an analog RF signaland into a digital baseband IQ signal according to a form of the DAS ina channel combiner.

In the case of the analog channel combining method, the multi-frequencyband and the multi-carrier signal may be bundled by outputting an RFsignal through an analog-to-digital converter (ADC) and adigital-to-analog converter (DAC) after the low physical layer 212 andan RF transceiver that converts a converted analog signal by radiofrequency (RF) and connecting the RF signal with a channel combiner, or,in the case of a millimeter wave frequency band, converting theconverted analog signal by an intermediate frequency (IF) and thenconnecting the IF signal to the channel combiner.

In the case of the digital method, digital baseband I/Q signalsextracted from a plurality of O-RAN RUs 200 and low physical layers 212may be mapped by a TDM method and processed in a bundle.

FIG. 2A is a schematic block diagram of a distributed antenna system(DAS) connected to a channel combiner CHC by an analog RF signal byapplying a function of an O-RAN-based remote unit (RU) according to anembodiment of the present disclosure. As shown in FIG. 2A, a CU 162 anda DU 164 are connected to the fronthaul network 100. A signal of thefronthaul network 100 is split and input to each of the plurality ofO-RAN RUs 200 for each of frequencies f₁, f₂, . . . , f_(n) according toan O-RAN fronthaul 110 based on an O-RAN split specification. Theplurality of O-RAN RUs 200 are connected in parallel to the fronthaulnetwork 100 according to the frequencies f₁, f₂, . . . f_(n). Theplurality of O-RAN RUs 200 are respectively converted into analog RFsignals according to allocated frequencies f₁, f₂, . . . , f_(n), andconnected to the channel combiner CHC 120. The channel combiner 120 isconnected to an optical distribution unit (ODU) 130. A plurality ofradio units (RUs) 140 are connected to the ODU 130.

FIG. 2B is a schematic block diagram of a DAS connected to a digitalchannel combiner 182 by a digital baseband I/Q signal by applying afunction of an O-RAN-based RU according to an embodiment of the presentdisclosure. That is, FIG. 2B shows the DAS connected to the digitalchannel combiner 182 by the digital baseband I/Q signal.

FIG. 2C is a schematic block diagram of a DAS according to anotherembodiment of the present disclosure. As shown in FIG. 2C, the DAS maybe connected to the analog channel combiner 180 by an analog RF signalthrough various technologies, i.e., the POI 30 like the conventionaltechnology, with respect to a connection method between the base stationtransceiver systems (BTSs) 10 and 20 and the DAS.

Alternatively, the DAS may be connected to the digital channel combiner182 by the digital baseband I/Q signal digitally or by applying a methodaccording to the O-RAN-based split option through a common public radiointerface (CPRI) or an open base station initiative (OBSAI) interface186. Selectively, as shown in FIG. 2C, the DAS may be connected to theODU 130 in a method in which the analog method and the digital methoddescribed above are flexibly mixed.

FIG. 3 is a schematic block diagram of a new radio (NR) base station 160including the O-RAN RU 200 according to the present disclosure. As shownin FIG. 3 , the NR base station 160 is connected to an external Internet150. Inside the NR base station 160, the CU 162 and the DU 164 connectedto the Internet 150, the fronthaul network 100, and the RU 200 areconnected in series. The O-RAN fronthaul 110 is applied to a signaltransmitted between the fronthaul network 100 and the O-RAN RU 200.

FIG. 4 is a schematic block diagram of the O-RAN RU 200 applicable toequal to or less than 6 GHz according to an embodiment of the presentdisclosure. As shown in FIG. 4 , the O-RAN RU 200 includes a controlunit 218, an L2 switch 220, the O-RAN interface 210, the low physicallayer Low PHY 212, an ADC and DAC 214, an IEEE-1588 clock 216, and anup/down converter (UDC) 320. As the O-RAN interface 210, an Ethernetinterface or an optical interface may be used. The O-RAN interface 210is connected to an Ethernet L2 switch for communication with internalprocessors, and includes FPGA hardware to accommodate the low physicallayer Low PHY 212.

The low physical layer 212 is configured to process an output signal ofthe O-RAN interface 210. In addition, the ADC and DAC 214 connected tothe low physical layer 212 are provided. The DAC outputs an inputdigital signal as a converted analog signal.

As a method of converting the converted analog signal into radiofrequency (RF), one of two methods may be applied. The first method is amethod of directly converting an analog signal converted by an RFtransceiver into RF (direct conversion method). The second method is amethod of converting the converted analog signal into an intermediatefrequency (IF) and then converting the IF back into RF (superheterodynemethod). To this end, the DAC outputs IF equal to or less than 4 GHz.

And, the IEEE-1588 clock 216 is included as an element. The IEEE-1588clock 216 is used for a synchronization operation of the O-RAN RU 200.

The RF signal generated by the UDC 320 is transmitted to a radio unit(RU) 300 located at a long distance through the analog channel combiner180 and the ODU 130, and an optical receiving unit (ORU) 230 receives anoptical signal inside the RU 300. The received signal is converted intoan electrical RF signal and includes a high power amplifier (HPA) 330and a low noise amplifier (LNA) 340. Thereafter, radio waves aretransmitted and received by a duplexer or filter 350.

FIG. 5 is a schematic block diagram of the O-RAN RU 200 applicable to amillimeter wave (mmWAVE) according to an embodiment of the presentdisclosure. As shown in FIG. 5 , the internal configuration of the O-RANRU 200 is the same as that of the O-RAN RU 200 of FIG. 4 .

The ORU 230, an IF-RF converter 240, an RF-millimeter wave converter252, an array antenna interface 254, and an array antenna 256 areprovided inside a millimeter wave radio unit (RU) 250.

The IF-RF converter 240 converts IF into RF equal to or greater than 6GHz and transmits the RF to the RF-millimeter wave converter 252.

The RF-millimeter wave converter 252 is a transceiver capable oftransmitting and receiving RF in millimeter wave (e.g., 28 GHz or 39GHz).

The array antenna interface 254 is connected between the RF-millimeterwave converter 252 and the array antenna 256. The array antennainterface 254 performs a beam steering technology and a beam formingtechnology. Beam steering is a technology that branches an RF signal,which is a signal source, to several antennas, and forms a beam thatmeets the conditions by adjusting the phase and signal amplitude (gain)for each antenna. Beam forming is a technology that forms a beam only inthe direction of a subscriber among a plurality of users. A plurality ofarray antenna interface modules are used for the array antenna interface254 for beam steering or beam forming of millimeter wave.

The array antenna 256 performs broadband transmission of RF.

The detailed description of the preferred embodiments of the presentdisclosure as described above is provided to enable those skilled in theart to make and practice the present disclosure. Although the above hasbeen described with reference to preferred embodiments of the presentdisclosure, it will be understood by those skilled in the art thatvarious modifications and changes may be made to the present disclosurewithout departing from the scope of the present disclosure. For example,those skilled in the art may use each of configurations described in theembodiments described above by combining the configurations with eachother. Accordingly, the present disclosure is not intended to be limitedto the embodiments presented herein but is to have the widest scopeconsistent with the principles and novel features disclosed herein.

The present disclosure may be embodied in other specific forms withoutdeparting from the spirit and essential characteristics of the presentdisclosure. Accordingly, the above detailed description should not beconstrued as restrictive in all respects but as exemplary. The scope ofthe present disclosure should be determined by a reasonableinterpretation of the appended claims, and all modifications within theequivalent scope of the present disclosure belong to the scope of thepresent disclosure. The present disclosure is not intended to be limitedto the embodiments presented herein but is to have the widest scopeconsistent with the principles and novel features disclosed herein. Inaddition, the claims that are not explicitly cited in the claims may becombined to form an embodiment or may be included as new claims byamendment after the filing of the present disclosure.

What is claimed is:
 1. A distributed antenna system (DAS) formulti-carrier and multi-frequency band based on an O-RAN standard in anopen radio access network (O-RAN)-based mobile communication network,the DAS comprising: an O-RAN remote unit (RU) connected to a fronthaulnetwork according to an O-RAN split option specification of base stationtransceiver systems (BTSs), and comprising a plurality of O-RAN RUs toaccommodate a plurality of carriers and a plurality of frequency bands;and a channel combiner to which outputs of the plurality of O-RAN RUsare combined, wherein the channel combiner is an analog combiner, theDAS further comprising: an optical distribution unit (ODU) connected tothe analog combiner; and a radio unit (RU) connected to the ODU, andwherein the RU comprises: an optical receiving unit (ORU) configured toreceive an optical signal from the ODU; a high power amplifier (HPA)configured to process the received optical signal; a low noise amplifier(LNA) configured to process the received optical signal; and a duplexeror filter configured to transmit an output of the HPA and an output ofthe LNA as radio waves.
 2. The DAS of claim 1, wherein the O-RAN RUcomprises: an O-RAN interface configured to communicate with thefronthaul network and meet the O-RAN split option specification; a lowphysical layer configured to process a signal of the O-RAN interface; ananalog-to-digital converter (ADC) and digital-to-analog converter (DAC)corresponding to a form of the channel combiner; and an up/downconverter (UDC) configured to convert a converted signal into radiofrequency (RF).
 3. The DAS of claim 2, wherein the O-RAN interface is anEthernet or optical interface.
 4. The DAS of claim 1, wherein thechannel combiner is at least one of an analog combiner and a digitalcombiner.
 5. The DAS of claim 4, wherein the channel combiner is theanalog combiner, the DAS further comprising a POI interface forconnection by an analog RF signal.
 6. The DAS of claim 4, wherein thechannel combiner is the digital combiner, the DAS further comprising adigital common public radio interface (CPRI)/open base stationinitiative (OBSAI) interface.
 7. The DAS of claim 1, wherein an outputsignal of the analog combiner is a signal equal to or less than 6 GHz.